Circuit provided with a protective function

ABSTRACT

The invention relates to a circuit provided with a protective function which contains at least two power contactors that have main make contact elements arranged in release current circuits ( 4 ). According to the invention, each main make contact element ( 11;  H 12;  H 13 ) of a power contactor is connected in series to a main make contact element (H 21;  H 22;  H 23 ) of another power contactor in the respective release current circuit ( 4 ). Each make contact element (S 1;  S 2 ) is provided in the coil current circuit ( 1; 1′ ) of each coil (K  1;  K 2 ) of each power contactor, whereby the make contact elements can be jointly actuated. The main make contact elements of each power contactor are spatially arranged between two auxiliary contact units which each have a make contact element (T 1;  T 3  or T 2;  T 4 ) and a break contact element (VI; V 3  or V 2;  V 4 ), and which are configured as positively driven contacts. The make contact elements of all auxiliary contact units are connected in series in a first indicator circuit ( 2 ), and the break contact elements of all auxiliary contact units are connected in series in a second indicator circuit ( 3 ). The main make contact elements and the contacts of the assigned auxiliary contact units are fixed on a common contact bridge ( 8 ).

[0001] This is a continuation application of PCT/EP00/02735 filed Mar. 29, 2000, the entire disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a circuit arrangement provided with a protective function, containing at least two power contactors which have main make contact elements arranged in released circuits, in each case one main make contact element of a power contactor being connected in series to a main make contact element of another power contactor in the respective released circuit.

RELATED ART

[0003] In circuit arrangements provided with protective functions, the goal is, on one hand, to recognize individual faults by carrying out the protective function but, on the other hand, to prevent unexpected starting as well. Protection against unauthorized, unintentional or erroneous closing of dangerous electric circuits should also be ensured. A circuit of the species mentioned at the outset which, however, contains positively driven relays, is known from German Patent DE 39 37122 C2. There, a so-called “fail-safe circuit” is implemented by a fail-safe AND gate which connects through to the coils of the positively driven relays only if the required safe condition exists, that is if none of the components is defective. In the case of power contactors, a positive drive of main and auxiliary contacts is not possible for design reasons.

SUMMARY OF THE INVENTION

[0004] Therefore, the object of the present invention is to provide a circuit arrangement with a protective function which fulfills the above mentioned criteria and which is suitable, in particular, for power contactors.

[0005] On the basis of a circuit arrangement of the type mentioned at the outset, this objective is achieved according to the present invention by the characterizing features of the patent claim.

[0006] According to the present invention, it is provided that in each case one make contact element be provided in the coil circuit of each coil of each power contactor, the make contact elements being able to be actuated jointly, and that the main make contact elements of each power contactor be arranged between two auxiliary contact units which each have a make contact element and a break contact element which are designed as positively driven contacts, the make contact elements of all auxiliary contact units being connected in series in a first indicator circuit and the break contact elements of all auxiliary contact units being connected in series in a second indicator circuit, and the contact elements of the power contactors and allocated auxiliary contact units being fixed on a common contact bridge.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Further details and advantages of the present invention ensue from the following exemplary embodiment which will be explained on the basis of Figures.

[0008]FIG. 1 is a schematized view of a circuit arrangement according to a specific embodiment of the present invention;

[0009]FIG. 2 shows the interconnection of the self-monitoring power contactors in a redundant design;

[0010]FIG. 3: is a schematic representation of a power contactor arranged between auxiliary contact units for the circuit arrangement according to the present invention, depicting a first fault where the main contacts of the power contactors are welded:

[0011]FIG. 4: is a schematic representation of a power contactor arranged between auxiliary contact units for the circuit arrangement according to the present invention, depicting a second fault where a contact of an auxiliary contact unit is welded.

BEST WAY OF IMPLEMENTING THE INVENTION

[0012] The circuit arrangement according to FIG. 2 contains two power contactors whose coils are denoted by K1 and K2. Each of coils K1, K2 is arranged in a circuit 1 or 1′, respectively, which can be closed by a make contact element S1 or S2 via interrogation circuit 7. Thus, make contact elements S1 and S2 do not directly act upon the power contactors but upon interrogation circuit 7 as a safety-related interruption for channels 1 and 2 (FIG. 2). This is illustrated in FIG. 1 by the hatchings for interrogation circuit 7 in lines 1 and 1′. Make contact elements S1 and S2 can be actuated by a manual momentary contact switch 5. The power contactors are arranged with their main make contact elements H11, H12, H13 and H21, H22, H23 in the released circuits (here jointly denoted by 4) between auxiliary contact units, each auxiliary contact unit containing a contact pair T1, V1; T3, V3; T2, V2; T4, V4 composed of a make contact element T1, T3, T2, T4 and a break contact element V1, V3, V2, V4. The contacts of each auxiliary contact unit are positively driven within themselves, that is the break contact element and the make contact element can never be both open or both closed during normal operation. Make contact elements T1, T3 and T2, T4, respectively, are connected in series and arranged in a first indicator circuit 2. This indicator circuit 2 provides information on the active position. Break contact elements V1, V3 and V2, V4, in turn, are connected in series and arranged in a second indicator circuit 3, respectively. This indicator circuit 3 provides information on the passive position. The information from indicator circuits 2 and 3 is monitored and evaluated by an interrogation circuit 7. Since the circuit arrangement provided with a protective function according to the present invention does not fulfill the requirement for disconnector properties, provision is made for a main switch 6 in released circuits 4.

[0013]FIG. 1 depicts the circuit arrangement in the de-energized state in which coils K1, K2 are de-energized, a current flows in indicator circuit 3 and indicator circuit 2 is interrupted. If momentary contact switch 5 is now actuated, make contact elements S1 and S2 are closed. Coils K1 and K2 are excited; the contactors pick up. In the process, make contact elements T1, T3 and T2, T4, respectively, close while break contact elements V1, V3 and V2, V4 open, respectively. Main make contact elements H11, H12, H13, H21, H22, H23 of released circuit 4 are closed. If momentary contact switch 5 is not actuated, the conditions of the de-energized state are, in the normal case, restored.

[0014]FIG. 2 depicts the redundant and self-monitoring interconnection of two power contactors. The components of the released circuits are denoted by K1M, K2M, those of auxiliary contactors by HK1, HK2, HK3, HK4. A timer component K1T used for start-up bridging for the power contactors has also positively driven contacts. Due to the redundant design, the functional reliability of the circuit is guaranteed even if one of the self-monitoring power contactors fails completely.

[0015]FIGS. 3 and 4 are schematic representations of faults. In each case shown is a main make contact elements of a power contactor which are arranged between two auxiliary contact units B1 and B2.

[0016]FIG. 3 shows the fault that one of main make contact elements H11 becomes welded. By the tilting of contact bridge 8, break contact element V3 can close again and would in principle signal a release. However, break contact element V1 which is arranged in the same indicator circuit 3 and situated in the spatial vicinity of main make contact element H11 remains open so that no current flows in indicator circuit 3, which is recognized by interrogation circuit 7 (FIG. 1). Accordingly, make contact element T3 opens but, since make contact element T1 remains closed, the fault is also recognized in indicator circuit 2. In the case of a welding of main make contact elements H12 and H13, the make and break contacts of the auxiliary contactors behave correspondingly.

[0017]FIG. 4 illustrates the situation when one of the contacts of an auxiliary contact unit becomes welded, here, by way of example, break contact element V1. Due to the strong pickup force, contact V1 bends, however, without opening, and all further contacts except for T1 go into their active position. However, the check of the active position via indicator line 2 signals the fault because of open make contact element T11 and the power contactor goes into the OFF position after a short start-up bridging via timer component K1T (FIG. 2).

[0018] The circuit arrangement of the present invention fulfills the requirement according to which an individual fault must be recognized by carrying out the protective function. Moreover, the circuit arrangement fulfills the requirements for breaking devices to prevent unexpected starting. In the case of a suitable design of the interrogation circuit, the requirements for protection against unauthorized, unintentional and/or erroneous closing are fulfilled as well. However, the circuit arrangement has no disconnector properties, therefore the main switch in the released circuits is still necessary.

[0019] The features of the present invention disclosed in the above specification, in the drawing as well as in the patent claim can be essential to the implementation of the present invention both alone and in an arbitrary combination. 

What is claimed is:
 1. A circuit arrangement provided with a protective function, containing at least two power contactors which have main make contact elements arranged in released circuits (4), in each case one main make contact element (H11; H12; H13) of a power contactor being connected in series to a main make contact element (H21; H22; H23) of another power contactor in the respective released circuit (4), wherein in each case one make contact element (S1; S2) is provided in the coil circuit (1; 1′) of each coil (K1; K2) of each power contactor, the make contact elements (S1; S2) being able to be actuated jointly, the main make contact elements (H11; H12; H13 and H21; H22; H23, respectively) of each power contactor are each spatially arranged between two auxiliary contact units (B1; B2) which each have a make contact element (T1; T3 and T2; T4, respectively) and a break contact element (V1; V3 and V2; V4, respectively) which are designed as positively driven contacts, the make contact elements (T1, T3, T2, T4) of all auxiliary contact units (B1; B2) being connected in series in a first indicator circuit (2), the break contact elements (V1, V2, V3, V4) of all auxiliary contact units (B1; B2) being connected in series in a second indicator circuit (3); and the main make contact elements (H11; H12; H13 and H21; H22; H23, respectively) and the contacts (T1, V1; T3, V3 and T2, V2; T4, V4, respectively) of the assigned auxiliary contact units (B1; B2) being fixed on a common contact bridge (8). 